A 60-kilometre ferry-ride north of Palermo, Ustica's name derives from a Latin word iustum/i, meaning 'burnt'. But this is a fertile island, full of flowers, vines, figs and lentils. Ustica is the summit of an underwater volcano, famed for its limpid waters, and the site of Italy's first marine national park. Glass-bottomed boats reveal submerged secrets. Shipwrecks, sea life, basalt caves and deep abysses create a scuba-diving paradise.